Golfdom, February 2019

THE ABCS OF ABW FIGURE 2A FIGURE 2B may inhibit either ABW adult or larval persistence in these areas Greenhouse and field plot trials confirmed our suspicions as 26 percent to 38 percent of adults were removed from the turfgrass canopy in a single mowing Mowing height had a significant impact on adult removal as the percent removed decreased at increasing mowing heights with practically no removal at collar height of cut The percentage of adults removed was encouraging given that the true impact is likely to be additive as greens are mowed five to seven days per week throughout the growing season However superintendents most likely cant rely on mowing alone as a stand alone tactic as we detected eggs in our lowest mowing height treatments 0100 inch that were capable of surviving to damaging stages We need a better understanding of adult behavior and movement within the turfgrass canopy to identify conditions or periods when mowing can have an even greater impact on adult populations on putting surfaces and higher mown areas fairways tees Therefore to optimize adult removal we initiated a second study to understand when weevils were on top of the turfgrass canopy and to identify periods when mowing would be most effective LABORATORY STUDIES Most animals exhibit diel patterns an increase in activity with regard to time of day or photoperiod that allow them to move feed escape predation or mate Our efforts to improve ABW mechanical removal through mowing required a better understanding of ABW surface activity and the factors that influence movement Our investigations sought to assess the effects of photoperiod light dark periods and temperature on adult activity It had been anecdotally reported by researchers that ABWs are nocturnal which was not surprising because many weevils become most active near dusk or in the middle of the night However making direct observations of ABW behavior is difficult because the weevil is relatively small 014 to 018 inch in length and requires tracking movement in darkness We initially observed weevil surface activity in growth chambers using time lapse photography To overcome the challenge of observing movement through both light and dark phases we marked weevils with a UV pen which caused the weevil to fluoresce under a black light Figure 1 This system allowed for near continuous observations under precise light and temperature conditions We found surface activity to be greatest between 59 degrees to 68 degrees F and equal light dark phases with few weevils active on the surface when temperatures were less than 50 degrees F We detected no differences in surface movement with regard to time of day In a second experiment we programmed incubators to exhibit different daytime and nighttime conditions 14 hours of light at 64 degrees F 10 hours of darkness at 50 degrees F such as those encountered in spring during the overwintering adult migration period These conditions resulted in diurnal activity with greatest activity around midday and little to no activity during the dark phase However when we reversed temperatures for light and dark phases 10 hours of light at 50 degrees F 14 hours of darkness at 64 degrees F we observed the opposite with the greatest activity in the middle of the night and little to no activity during the light phase suggesting that temperature not photoperiod had a greater impact on surface activity Continued on page 36 February 2019 Golfdom 35 Golfdom com PHOTOS BY CHARLES MAZEL Two ABWs marked with a Sharpie Neon bottom and two unmarked weevils photographed without the filter system A The same weevils were photographed with the NIGHTSEA system B The black light illuminated the mark during dark periods

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